Heterophasic Polypropylene

Impact Morphology

Mechanical performance depends on the controlled dispersion of ethylene-propylene rubber particles within the rigid matrix. High impact strength arises when rubber particle size distribution remains narrow during the injection moulding process. Large particles cause internal stress concentrations that trigger premature part failure under heavy loads.

Small, uniform particles improve toughness without sacrificing the inherent stiffness of the base resin.

Thermal Processing

Injection moulding cycles require tight control over melt temperatures to prevent rubber degradation. High shear rates during fill encourage particle deformation that alters the final impact resistance of a finished product. If the barrel temperature exceeds recommended limits, the rubber phase loses its ability to absorb mechanical shocks.

Consistency across a production run depends on managing back pressure to ensure uniform dispersion throughout the cavity.

Regrind Economics

Manufacturers incorporate recycled material to reduce costs but must account for the dilution of mechanical specifications. Virgin resin contains a precise ratio of rubber to matrix that degrades during initial thermal exposure. Multiple heating cycles reduce the effective elasticity of the rubber phase.

Parts requiring high impact performance frequently restrict regrind usage because the mechanical property drop occurs linearly with each pass through the machine.